A. Field
The present invention concerns a device for simultaneously cooling and removing liquid from compressed gas of a compressor element or of several compressor elements which are connected either or not in parallel and/or in series, which device comprises a pressure vessel erected in the compressed air line and which is provided with a liquid drain at the bottom, an inlet for compressed gas at a distance above the latter and a gas outlet at the top.
B. Related Art
In a liquid-injected compressor element is injected water, oil or another liquid in the inlet air or in the rotor chamber for lubrication, cooling and sealing. The liquid is discharged together with the compressed gas and subsequently separated in a pressure vessel and cooled in a heat exchanger, after which it is injected again in the compressor element.
When a gas, comprising vapours such as water vapour, is compressed and subsequently cooled, it may contain less of these vapours as the relative contribution of the vapour pressure of these vapours to the total pressure decreases. In many cases, this results in the compressed gas being saturated with these vapours and a part of the vapours being condensed during the cooling of the compressed gas.
For many applications, the presence of condensate in the compressed gas is very detrimental and the risk of damage is large when the gas is saturated with vapour. That is why a condensate separator is provided in compressors following the gas cooler, as well as an extra gas drier in many cases, i.e. a device for lowering the partial pressure of the vapour in the compressed gas. This gas drier in many cases consists of a gas cooler which cools the gas to the required dew point of the vapours and an extra condensate separator after which the gas is heated again.
From European patent 0,120,547, such a gas drier is known in which compressed air is dried in this case by means of direct contact with icy water which bubbles up.
The disadvantage of this gas drier is that the heat transfer is not very efficient and that moreover ice can be formed, which results in a large thermal resistance being built up which makes sure that the energy is used even less efficiently.
Another disadvantage of the gas drier from EP 0,120,547 is that use is made of an all-air heat exchanger which is inherently characterised by a high pressure drop in relation to the recycled energy.
A disadvantage of gas coolers in general is that they have to resist the high pressure of the compressed gas, that they are relatively expensive and cause a relatively large pressure loss of the compressed gas.
Condensate separators are either a relatively major source of pressure loss of the compressed gas, or they are not very efficient. This is all the more true when the flow of the compressed gas can strongly vary, as is for example the case with compressors with a variable rotational speed.
The heat exchangers of gas driers have to resist the high pressure of the compressed gas, they are voluminous and relatively expensive. These heat exchangers, as well as the condensate separators of gas driers are a relatively major source of pressure loss for the compressed gas.
Moreover, the assembled device of the gas cooler, condensate separator and gas drier requires several connecting pipes which further increase the cost price of the device, as well as the pressure loss of the compressed gas.